Means for stretching a resonant plate over a frame.



F. FRANKEL.

MEANS FOR STRETGHING A RESONANT PLATE OVER A FRAME.

' APPLICATION TILED JULY 18, 1912.

1 ()78 424 Patented Nov. 11, 1913.

2 SHEETSSHEET l.

Ira/vendor. Eat/01f Z/ mie] F. FRANKBL.

MEANS FOR STRETGHING A RESONANT PLATE OVER A FRAME.

APPLICATION FILED JULY 18 1912.

Patented Nov. 11, 1913.

2 SHEETS-SHEET 2.

UNITED STATES PATENT OFFICE.-

FRIDOLF FRANKEL, OF STOCKHOLIVI, SWEDEN.

MEANS FOR STRETCEIING A. RESONANT PLATE OVER A FRAME.

To all whom it may concern:

Be it known that I, F RIDOLF FRANKEL, a subject of the King of Sweden, residing at Stockholm, in the Kingdom of Sweden, have invented new and useful Improvements in Means for Stretching a Resonant Plate over a Frame, of which the following is a speci fication, reference being had to the drawing accompanying and forming a part hereof.

My invention relates to improvements in means for stretching a resonant plate over a frame for instance in pianos or other string instruments, especially such a plate as is constructed from sheet metal.

The main object of my invention is to provide means for stretching the plate in a most uniform manner, and, if so desired, with stronger tension in the treble, or the part of the plate intended for the highest tones. To gain this object I fasten a plurality of stretching levers to the edges of the plate, and provide means for attaching the stretching levers to the frame and also means for adjusting the position of the stretching levers relatively to the frame. Whether the said stretching levers should be attached first to the plate or to the frame depends partly on the form of the stretching levers and partly on other circumstances such as the available space, and so forth. The stretching levers are provided with means, such as hooks or screws, for attaching them to the frame, and with other means, as wedges or screws, for stretching the plate or for putting tension upon the same.

My invention is illustrated in the accompanying drawing, in which Figures 1 to at show in sectional views several ways of applying the invention to the plate and frame of a piano. Fig. 5 illustrates the arrangement shown in Fig. 4fin a view at right angles to said figure.

Referring to the drawings, 2 represents the resonant plate, made of sheet metal, and provided along its edges with lugs or tongues 3, which by means of screws 1, or

Specification of Letters Patent.

Application filed July 18, 1912.

Patented Nov. 11,1913.

Serial No. 710,298.

by soldering, are securely fastened to stretching levers 5. These are attached all around to the frame 1, with a suitable distance between the different stretching levers.

In Fig. l the stretching lever is formed with a hook 6, arranged to engage the edge 7 formed in the frame 1. The stretching of the plate is done by means of the set-screws 8 which are threaded through the stretching lever and rest with their ends in a groove in the frame 1. If desired more than one of such set-screws 8 can be used in each stretching lever.

In the modifications shown in Figs. 2 and 3 the hook 6 is substituted by a screw 9 passing through the stretching lever and threaded through the edge of the frame 1. This screw serves as an adjustable support for the stretching lever and at the same time as a means for stretching the plate. The stretching can also be done by the setscrew 8 threaded through the frame 1 and ar ranged to press outward the upper part of the stretching lever. In Fig. 3 a wedge 10 is used instead of the aforesaid setscrew 8.

In Figs. 4 and 5 the stretching lever is fulcrumed on an edge 11 formed upon the outside of the frame 1, and the stretching of the plate is done by tightening the nut 12 of the screw-bolt 13, which passes freely through a hole in the frame.

The above described means for stretching the resonant plate possesses also the advantage that there are no parts extending far beyond the edge of the plate, which advantage is quite important in the manufacture of grand pianos.

WVhat I claim is:

1. The combination of a resonant plate, a frame, a plurality of stretching levers fastened to the edges of the plate, means for attaching the stretching levers movably to the frame, and means for moving the stretching levers so as to stretch the plate.

2. The combination of a resonant plate, a frame, stretching levers fastened to the edges of the plate and fulcrumed on the frame, said resonant plate being fastened to the stretching levers, and means for moving levers, and it screw passing through each mg the stretclnng levers so as to stretch the stretching lever and the frm'ne adapted to 10 plate. move the stretching lever so as to stretch the 3. The combination of aresonant plate, a plate. 7

frame provided with an edge, stretching FRIDOLF FRANKEL.

levers fastened to the edges of the plate and lVitnesses:

fulcruniecl on the ecl 'e of the frame, said FREDR. LTORDSJ6,

resonant plate being Iastened to the stretch- O. M. SANDELL.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, I). C. 

